Spinal rod connector

ABSTRACT

A rod connector for joining a first rod and a second rod includes bore holes that are offset and/or non-parallel to each other. The rod connector provides an offset or non-parallel connection between the rods that allows for the rods to match the contour of a patient&#39;s body without requiring bending of the rods. The rod connector may include a first bore hole for receiving the first spinal rod and a second bore hole for receiving the second spinal rod that is adjustable relative to the first bore hole to adjust the position and/or orientation of the second spinal rod relative to the first spinal rod. The rod connector may comprise a first housing component defining the first bore hole and a second housing component that is movable relative to the first housing component and defining the second bore hole.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentContinuation application Ser. No. 14/334,994, filed Jul. 18, 2014,entitled “SPINAL ROD CONNECTOR”, which claims priority to U.S. PatentContinuation application Ser. No. 13/540,770, filed Jul. 3, 2012,entitled “SPINAL ROD CONNECTOR” (Now U.S. Pat. No. 8,852,237), whichclaims priority to U.S. Non-Provisional application Ser. No. 10/815,883,filed Mar. 31, 2004, entitled “SPINAL ROD CONNECTOR”, (Now U.S. Pat. No.8,236,028), all applications are herein incorporated by reference intheir entireties.

FIELD OF THE INVENTION

The present invention relates to a spinal fixation systems used toretain positions of a spinal column, such as vertebrae, in a desiredspatial relationship. More particularly, the present invention relatesto a component of a spinal fixation system for connecting a first rod toa second rod.

BACKGROUND OF THE INVENTION

Spinal fixation systems may be used in surgery to align, adjust and/orfix portions of the spinal column, i.e., vertebrae, in a desired spatialrelationship relative to each other. Many spinal fixation systems employa spinal rod for supporting the spine and for properly positioningcomponents of the spine for various treatment purposes. Vertebralanchors, comprising pins, bolts, screws, and hooks, engage the vertebraeand connect the supporting rod to different vertebrae.

The length of the cylindrical rod depends on the size and number ofvertebrae to be held in a desired spatial relationship relative to eachother by the apparatus. The rods may be bent, as desired, to conform toa desired curvature of the spinal column in one or more of the anatomicplanes. The size of the spinal rod depends on the region of the spinewhere the spinal fixation system is used. For example, in the cervicalregion of the spine, where the vertebrae tend to be smaller, arelatively smaller spinal rod is used, which is positioned close to thecenter of the spine. In the thoracic region, where heavier loads areexperienced and the vertebrae tend to be larger, a rod having a largerdiameter is used. The cervico-thoracic junction of the spine istypically fused using rods of two different diameters to accommodateanatomical differences between the cervical and thoracic spine regions.To accommodate a system including spinal rods having different sizes andconfigurations, a rod connector may be used to join a first rod and asecond rod. The rod connector may be a side-by-side connector, where theends of the two rods are placed side-by-side and connected using aconnector that spans the two ends, or an axial connector, which alignsthe axes of the two rods and connects the ends of the rods togetheralong the axial direction.

Prior rod-to-rod connectors for the cervico-thoracic junction are staticand include fixed, parallel bore holes for receiving spinal rods thatare spaced an equal distance from the spinal column, i.e., having axesthat are aligned in the sagittal plane of the patient when the connectoris implanted. However, the spinal support rods that are joined using arod connector are frequently oriented at various angles and positionsdue to the anatomical structure of the patient, the physiologicalproblem being treated, and the preference of the physician. Because thetwo rods are configured to accommodate variations in the spinal column,the portions of the rods that are connected by the connector may not beparallel to each other, or spaced the same distance from the spinalcolumn. The discrepancy must be fixed by bending the rods in otherregions, such that the portions that insert in the bore holes arealigned and parallel with each other. However, bending tends to weakenthe rods and can be an imprecise method for ensuring that the rods fitin the connector.

SUMMARY OF THE INVENTION

The present invention provides an improved rod connector in a spinalfixation system for connecting a first spinal rod to a second spinalrod. The rod connector provides an offset or non-parallel connectionbetween the rods that allows the rods to match the contour of apatient's spinal column without requiring bending of the rods. The rodconnector may include a first bore hole for receiving the first spinalrod and a second bore hole for receiving the second spinal rod that isadjustable relative to the first bore hole to adjust the position and/ororientation of the second spinal rod relative to the first spinal rod.The rod connector may comprise a first housing component defining thefirst bore hole and a second housing component that is movable relativeto the first housing component and defining the second bore hole. Thesecond bore hole may be made adjustable using a spherical bushing toallow a spinal rod received in the second bore hole to pivot within thebore hole to adjust the position of the spinal rod relative to the firstspinal rod.

According to a first aspect of the invention, a connector for connectinga first rod and a second rod comprises a housing component and a lockingelement. The housing component defines a first bore hole for receiving aportion of the first rod and a second bore hole for receiving a portionof the second rod. The first bore hole extends along a firstlongitudinal axis and the second bore hole extends along a secondlongitudinal axis. The locking element secures one of the first rodwithin the first bore hole and the second rod within the second borehole. The first longitudinal axis is offset from the second longitudinalaxis by a predetermined offset distance.

According to another aspect of the invention, a connector for connectinga first rod and a second rod comprises a housing component and a lockingelement. The housing component defines a first bore hole for receiving aportion of the first rod and a second bore hole for receiving a portionof the second rod. The first bore hole extends along a firstlongitudinal axis and the second bore hole extends along a secondlongitudinal axis that is non-parallel with the first longitudinal axis.The locking element secures one of the first rod within the first borehole and the second rod within the second bore hole.

According to another aspect of the invention, a connector for connectinga first rod and a second rod comprises a first housing componentdefining a first bore hole for receiving a portion of the first rod anda second housing component coupled to the first housing component. Thesecond housing component defines a second bore hole that is movablerelative to the first bore hole for receiving a portion of the secondrod.

According to another aspect of the invention, a method of connecting afirst rod to a second rod, comprises the steps of inserting the firstrod into a first bore hole of a rod connector, inserting the second rodinto a second bore hole of the rod connector and moving the second borehole relative to the first bore hole.

According to still another aspect, a connector for connecting a firstrod and a second rod comprises a housing component, which defines afirst bore hole for receiving a portion of the first rod and a secondbore hole for receiving a portion of the second rod, and a lockingelement for securing one of the first rod within the first bore hole andthe second rod within the second bore hole. A first longitudinal axis ofthe first bore hole is configured to be offset from a secondlongitudinal axis of the second bore hole in a first plane by a firstpredetermined offset distance and by a second predetermined offsetdistance in a second plane that is perpendicular to the first plane.

According to another aspect, connector for connecting a first rod and asecond rod is provided, which comprises a housing component having a topsurface, a bottom surface, a front surface and a back surface and alocking element inserted through the top surface for securing one of thefirst rod within a first bore hole defined by the housing component andthe second rod within a second bore hole defined by the housingcomponent. The first bore hole is offset from the second bore hole, suchthat said first bore hole is closer to the bottom surface of the housingthan the second bore hole

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a rod connector including off-set bore holes forreceiving rods according to an embodiment of the invention.

FIG. 2 illustrates a rod connector including non-parallel bore holes forreceiving rods according to another embodiment of the invention.

FIG. 3 illustrates a rod connector comprising adjustable housingcomponents defining bore holes for receiving rods according to anotherembodiment of the invention.

FIGS. 4A-4E illustrate different views of a rod connector comprisingfirst and second housing components including a coupling rod forrotatably coupling the first housing component to the second housingcomponent.

FIG. 5 illustrates an embodiment of a compression chip for use with arod connector having a coupling rod.

FIGS. 6A-C illustrates different views of an alternative embodiment ofthe rod connector of FIGS. 4A-4E, wherein the coupling rod includesinterlocking teeth.

FIG. 7 illustrates a rod connector including pivotably mounted housingcomponents.

FIGS. 8A-8D illustrates different views of a rod connector including aspherical bushing in a bore hole for adjusting a longitudinal axis ofthe bore hole.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an improved rod connector for connectinga first rod and a second rod in a region of the spine, such as thecervico-thoracic junction region of the spine. The rod connector of thepresent invention reduces or eliminates the need for bending connectedrods. The invention will be described relative to illustrativeembodiments, though one skilled in the art will recognize that theinvention is not limited to the described embodiments. While the rodconnector is used primarily in the cervico-thoracic junction region ofthe spine, the rod connector may also be employed to couple any type ofcomponent used in an orthopedic implant system.

FIG. 1 illustrates a rod connector 10 for connecting a first spinal rod,such as a cervical rod, and a second spinal rod, such as a thoracic rod,in a cervico-thoracic junction region of the spine according to anembodiment of the present invention. The rod connector 10 may be used inan occipito-cervico-thoracic spinal fixation system for rigid posteriorfixation of the occipito-cervico-thoracic regions of the spine, thoughthe rod connector may alternatively be used in any suitable location toconnect any suitable components of an orthopedic system.

The rod connector 10 includes a housing 12 defining a first bore hole 22for receiving a portion of the first rod and a second bore hole 32 forreceiving a portion of the second rod. Preferably, the rod connector 10receives the end portions of each rod, though one skilled in the artwill recognize that the rod connector can connect any suitable portionof a rod. The housing may be formed of any suitable bio-compatiblematerial, including, but not limited to stainless steel, titanium,plastic, and mixtures thereof.

According to the illustrated embodiment, each bore hole 22, 32 is formedby a pair of circular openings having centers which are offset along acentral axis, such that each bore hole has a generally ovalcross-sectional configuration. The size of the circular openings whichcooperate to form the rod bore holes are such that the associated rodcan move between the upper and lower portion of the bore hole. The lowercircular opening is preferably slightly smaller in diameter than theassociated rod, to provide an interference fit between the housing andthe rod when the rod is inserted in the lower circular opening. Forexample, the first bore hole 22 may be configured to receive a cervicalrod, which has a diameter of less than about 4 millimeters andpreferably between about 2.5 millimeters and about 3.5 millimeters. Thesecond bore hole 32 may be configured to receive a thoracic rod, whichhas a diameter of between about 4.75 millimeters and about 6.35millimeters and preferably about 3.5 millimeters.

One skilled in the art will recognize that the shape and size of thebore holes is not limited to the illustrated embodiment, and that thebore hole may have any suitable size and/or shape for receiving a rod.For example, the bore holes may alternatively have a circular orpolygonal cross-section.

The rod connector 10 further includes a locking mechanism 40 forsecuring one or both of the rods to the housing 12. In the illustratedembodiment, the locking mechanism 40 comprises a first set screw 42disposed in a first screw passage 44 that extends traverse to andintersects with the first bore hole 22 and a second set screw 46disposed in a second screw passage 48 that extends traverse to andintersects with second bore hole 32. To secure each rod to the rodconnector 10, the each set screw is tightened in the associated setscrew passage after the rod is inserted in the bore hole. As the setscrew is tightened, force is transmitted from the set screw to the rodto secure the rod within the bore hole.

In the embodiment shown in FIG. 1, the first bore hole 22 has a firstcentral longitudinal axis -A-A- along which the first bore hole 22extends and the second bore hole has a second central longitudinalcentral axis -B-B- along which the second bore hole 32 extends. The boreholes 22, 32 are offset from each other, such that when the rodconnector 10 is inserted in a patient, the -B-B- axis of the second borehole 32 is offset from the -A-A- axis of the first bore hole 22 in thesagittal plane, i.e., the longitudinal plane that divides the body of abilaterally symmetrical animal into right and left sections. (Thesagittal plane is parallel to the YZ axis shown in FIG. 1). The offsetof the bore holes in the sagittal plane positions one of the bore holes,illustrated as the second bore hole 32, closer to the spine and thebottom surface of the connector than the other bore hole. As shown, theaxis -B-B- of the second bore hole is offset from the axis -A-A- of thefirst bore hole by a first predetermined distance W in a first plane,and by a second predetermined distance D in a second plane, which alignswith the sagittal plane, that is perpendicular to the first plane. Asshown, the first plane is parallel to the XY plane and the second planeis parallel to the YZ plane.

The rod connector 10 of FIG. 1 contrasts conventional spinal rodconnectors, in which the longitudinal axes of the bore holes are alignedin the sagittal plane, i.e., the same vertical distance from the spine.By offsetting the longitudinal axes of the bore holes in a verticaldirection, the ends of the first and second rods can be placed varyingdistances from the spine without requiring the surgeon to bend one ormore of the rods to accommodate a particular spinal configuration. Thelongitudinal axis -A-A- may be parallel to the offset axis -B-B-, or theaxes may be skewed relative to each other. The offset distance D may beany suitable distance depending on a particular application. In theembodiment of FIG. 1, the first bore hole 22 is placed closer to thespine than the second bore hole 32 by the distance D, though one skilledin the art will recognize that the second bore hole 32 may alternativelybe positioned closer to the spine than the first bore hole.

According to one aspect, a surgeon can select an appropriate rodconnector having a suitable offset distance from a selection of rodconnectors having different offset distances, based on a particularspinal configuration.

According to another embodiment of the invention, shown in FIG. 2, a rodconnector 100 may include bore holes that extend along longitudinal axesthat are non-parallel, such that the portions of the rods seated withinthe connector are non-parallel to each other. The rod connector 100includes a housing 112 defining a first bore hole 122 extending along afirst longitudinal axis -AA-AA- for receiving a first spinal rod and asecond bore hole 132 extending along a second longitudinal axis -BB-BB-for receiving a second spinal rod.

The second longitudinal axis is skewed relative to the firstlongitudinal axis to allow the rods to extend in a non-paralleldirection. The longitudinal axis of each bore hole may extend at anysuitable angle to accommodate a particular spinal configuration. Forexample, the first bore hole 122 can extend in a direction that isparallel to the longitudinal axis of the spine, while the second borehole is angled relative to the longitudinal axis of the spine and thefirst bore hole. Alternatively, both bore holes may be skewed relativeto the axis of the spine. One skilled in the art will recognize that thefirst and second bore holes may extend at any suitable angle relative tothe longitudinal axis and/or each other, depending on the particularcurvature of the spinal column. In addition, the first longitudinal axis-AA-AA- and the second longitudinal axis -BB-BB- may be aligned relativeto the spine or offset, as shown in FIG. 1.

According to one aspect, a surgeon can select an appropriate rodconnector having suitable bore hole angles from a selection of rodconnectors having bore holes extending at a variety of different angles,based on a particular spinal configuration

FIG. 3 illustrates a rod connector 200 comprising a plurality of housingcomponents that are movable with respect to each other to adjust theposition, angle or orientation of the rods relative to each other,according to another embodiment of the invention. The rod connector 200allows a surgeon to modify the connector to accommodate a particularjunction region, without permanently altering the connector and/or therods. The rod connector 200 comprises a first housing component 202including a first bore hole 222 for receiving a first rod 220 and asecond housing component 204 coupled to the first housing component 202and including a second bore hole 232 for receiving a second rod 230.

A locking mechanism 240 is also provided for securing one or both of therods to the housing. In FIG. 3, the locking mechanism 240 comprises afirst set screw 242 disposed in a first set screw passage 244 forsecuring the first rod 220 and a second set screw 246 disposed in asecond set screw passage 248 for securing the second rod 230.

The rod connector 200 further includes a coupling mechanism 280 formovably coupling the first housing component 202 to the second housingcomponent 204 to thereby connect the first rod and the second rod. Inthe embodiment shown in FIG. 3, the coupling mechanism 280 comprises afirst set of external teeth 281 on an outside surface 282 of the firsthousing component 202 and a second set of external teeth 283 on anoutside surface 284 of the second housing component that faces theoutside surface 282 of the first housing component. The first and secondsets of external teeth mesh to set the position of first housingcomponent and second housing component in a vertical direction.

A clamping mechanism 290 may also be provided for clamping the twohousing components 202, 204 together after the coupling mechanism 280places the first and second housing components into a selected positionrelative to each other. The clamping mechanism 290 may comprise anysuitable means for securing the second housing component 204 relative tothe first housing component 202, including, but not limited to one ormore screws, adhesive and a crimping tool.

The coupling mechanism 280 may enable relative movement of the firsthousing component relative to the second housing in one or more suitabledirections. For example, in the embodiment shown in FIG. 3, the couplingmechanism 280 comprises interlocking teeth connect at discrete locationsto vary the offset distance D of the central longitudinal axis of thefirst and second bore holes, thereby varying the elevation of one ormore of the rods relative to the spine. However, the coupling mechanism280 may alternatively allow the first housing component to rotaterelative to each other to vary the angle between the bore holes, or varythe lateral distance between the housing components to vary the distancebetween the bore holes. One skilled in the art will recognize that anysuitable means may be used to alter the orientation of the first borehole relative to the second bore hole in the rod connector 200 of FIG.3.

The use of adjustable housing components in a rod connector allows auser to adjust the relative position and/or orientation of the connectedspinal rods without replacing or damaging the rod connector. Therelative position and/or orientation of the bore holes can be adjustedbefore the spinal rods are inserted in the rod connector, after one ofthe spinal rods is inserted in the rod connector, or after both of thespinal rods have been inserted in the rod connector. For example,according to one embodiment, a surgeon may select an initial orientationof the bore holes by selectively positioning the housing componentsrelative to each other. After implantation of the spinal fixationsystem, the surgeon may readjust the rod connector housing components tovary the relative position of the bore holes to accommodate changes inthe contour of the spine over time.

As shown in FIGS. 4A-E, a coupling mechanism 380 for a rod connector ofthe present invention can alternatively comprise a protrusion extendingfrom one of the housing components and a recess on the other housingcomponent configured to receive the protrusion. For example, in the rodconnector 300 shown in FIGS. 4A-E, a transversely extending coupling rod381 on one of the housing components, illustrated as the first housingcomponent 302, cooperates with a coupling opening 382 on the otherhousing component, illustrated as the second housing component 304. Thecoupling opening 382 is sized and dimensioned to receive the couplingrod 381.

The coupling mechanism 380 allows the first housing component 302 tomove both laterally and angularly relative to the second housingcomponent 304 before and/or after implantation of the rod connector in apatient. For example, the lateral distance between the bore holes 322,332, and thus the rods joined by the connector 300 can be adjusted byadjusting the depth of insertion of the coupling rod 381 within thecoupling opening 382 to control the distance between the two housingcomponents. The angular position of the bore holes 322, 332, relative toeach other can be adjusted by rotating the first housing component aboutcoupling rod pivot the first housing component 302 relative to thesecond housing component 304. In the illustrative embodiment, thecoupling rod 381 has a circular cross section to allow infinite rotationin the sagittal plane, while facilitating medial/lateral adjustmentbetween the rods.

The rod connector of the present invention may further includes a rodseat in one or both of the housing components for seating a rod in thebore hole of the housing component.

In the embodiment shown in FIGS. 4A-E, the rod seat comprises a lateralgroove 364 on the coupling rod 381 for directly seating the spinal rod330 thereon.

As shown in FIG. 4B, the housing components 302, 304 may further includeoptional external teeth 381, 383, respectively, to facilitate couplingof the housing components. The teeth 386, 387 provide discrete positionsfor the housing components relative to each other, while increasing thecoupling strength between the housing components.

Alternatively, the rod seat may comprise a compression chip 360, shownin FIG. 5, disposed between the rod 330 of the second housing componentand the coupling rod 381 of the first housing component 302 when the rodconnector 300 is assembled. The compression chip 360 of the illustratedembodiment comprises an arc-shaped component forming a bottom channel361 that is complementary to the coupling rod 381 and having a topgroove 362 that is complementary to the bottom of the associated rod330. Advantages of using a compression chip, such as the compressionchip 360 shown in FIG. 5, include a greater surface area contact betweenthe rod 330 of the second housing component and the coupling rod 381,which provides a more stable connection between the housing components.The compression chip 360 also facilitates media-lateral translationbetween the housing components to vary the distance between the rods ina media-lateral plane.

The spinal rod may alternatively be directly seated on the insertedcoupler rod through point-on-point contact when the rod connector isassembled. One skilled in the art will recognize that the rod seat mayhave any suitable configuration and location for seating a spinal rod.

After the housing components are positioned relative to each other usingthe coupling mechanism 380, a clamping mechanism secures the position ofthe first housing component 302 relative to the second housing component304. In the embodiment shown in FIGS. 4A-E, the clamping mechanism forsecuring the housing components is also a locking mechanism for securingthe spinal rods in the respective bore holes. After assembly andpositioning of the housing components 302, 304 relative to each other ina selected position and insertion of the spinal rods 320, 330 in therespective bore holes 322, 332, respectively, a first set screw 342 isinserted in a first screw passage 344 and a second set screw is 346inserted in a second screw passage 348. The second set screw 346 istightened to compress the second spinal rod 330, the rod seat and thecoupling rod 381 together to secure the position of the coupling rodwithin the coupling passage and lock the spinal rod 330 within the borehole 332. The first set screw 342 is also tightened to secure the firstspinal rod 320 in the first bore hole 322.

In the embodiment of FIGS. 4A-E, the coupling opening 382 extendsthrough the second housing component 304 and the coupling rod 381extends through the second housing component 304 when the two housingcomponents are positioned adjacent to each other. However, one skilledin the art will recognize that the coupling opening 382 and coupling rodmay have any suitable size, length and configuration for coupling thefirst housing component to the second housing component in a selectedposition and orientation.

While the embodiment of FIGS. 4A-E illustrates the coupling rod 381 as aprotrusion extending from the first housing component 302 below andtransverse to the first bore hole 322 and the coupling hole 382 as apassageway extending below and transverse to the second bore hole 332 inthe second housing component 304, one skilled in the art will recognizethat the invention is not limited to the illustrated configuration. Forexample, the coupling rod may alternatively be provided on the secondhousing component and the corresponding coupling hole may be provided onthe first housing component. The coupling rod and coupling hole may alsobe provided above or below the corresponding bore hole.

As shown in FIGS. 6A-6C, a rod connector 300′ may include a coupling rod381′ having external teeth 384 configured to cooperate with teeth 385 onthe coupling opening 382′. The use of interlocking teeth increased thecoupling strength between the housing components, while providingdiscrete rotation positions between the housing components.

According to yet another embodiment of the invention, as shown in FIG.7, a rod connector 400 for coupling a first rod 420 to a second rod 430may comprise a plurality of housing components 402, 404 that arepivotably mounted to a connecting component 480. The first housingcomponent 402 includes a first bore hole 422 for receiving the first rod420 and the second housing component 404 includes a second bore hole forreceiving the second rod 430. One or both of the housing component 402,404 is rotatably mounted to a transversely extending connectingcomponent 480 using screws 442, 444 or other suitable means. Therelative position of the housing components is adjusted by rotating eachhousing component about the axis of the screws 442, 444 to vary theangle of each bore hole 422, 432 relative to each other and thelongitudinal axis of the spine. After pivoting each housing componentinto a selected position, the screws 442, 444 are tightened to lock theposition of each housing component 402, 404, respectively, therebycreating a rigid rod connector for fixing the position of the first rod420 and the second rod 430 relative to each other.

According to another embodiment of the invention, as shown in FIGS.8A-8D, a rod connecter 500 may include a spherical bushing in one ormore of the bore holes for receiving a spinal rod to allow thecorresponding spinal rod to move relative to the housing of the rodconnector. For example, in the embodiment shown in FIGS. 8A-8D, the rodconnector 500 comprises a top housing component 506 defining a top halfof a first bore hole and a top half of a second bore hole. The rodconnector 500 also includes a bottom housing component 508 defining abottom half of the first bore hole and a bottom half of the second bore.The top housing component 506 and bottom housing component cooperate todefining a first bore hole 522 for receiving a first spinal rod 520 anda second bore hole 532 for receiving a second spinal rod 530 whenassembled together. A spherical bushing 580 is providing in one of thebore holes, illustrated as the first bore hole 522, around theassociated spinal rod 520 for allowing the spinal rod to move relativeto the housing 506. The bushing 580 thus allows for the position of thefirst spinal rod to be adjusted relative to the position of the secondspinal rod without bending or modifying the rods.

After moving the first spinal rod 520 into a selected position relativeto the housing 506 and second spinal rod 530, the housing components arefixed using a locking mechanism, illustrated as a top-loading set screw542 disposed in a screw passage 544 extending between the top housing506 component and the bottom housing component 508. The screw 542, whentightened, locks the housing components together, fixing the spinal rods520, 530, within the bore holes 522, 532, respectively, and fixing theposition of the first spinal rod 520, as defined by the orientation ofthe spherical bushing 580, relative to the second spinal rod 530.

According to an alternate embodiment, a locking mechanism for securingthe position of the spinal rods within the rod connector may comprise aplurality of screws. For example, the locking mechanism may comprise afirst screw and a second screw disposed on the outside of the bore holesfor locking the housing components together and fixing the relativepositions of the spinal rods.

The housing of the rod connector 500 is also not limited to a top andbottom housing component and may alternatively comprise a unitaryhousing component defining the first and second bore holes, or othersuitable configuration.

While the invention has been described relative to a side-by-side rodconnector, one skilled in the art will recognize that the principles andconcepts of the invention also apply to an axial connector having boreholes arranged on opposite ends of the connector and facing differentdirections. Examples of such end-to-end connectors are described incommonly owned U.S. Ser. No. 10/708,919 (U.S. Pat. No. 7,909,852),entitled “Adjustable-Angle Spinal Fixation Element”, the contents ofwhich are herein incorporated by reference.

The rod connector of the present invention provides significantadvantages over prior rod connectors for connecting two spinal rods. Therod connector accommodates variations in the contour of the spine indifferent regions without bending and subsequent weakening of the spinalrod. The rod connector allows a surgeon to precisely select and adjust,if necessary, the angle and/or distance between the two bore holesreceiving the spinal rods. In this manner, the rod connector facilitatesalignment, adjustment and/or fixation of the vertebrae in a desiredspatial relationship relative to each other.

The present invention has been described relative to an illustrativeembodiment. Since certain changes may be made in the above constructionswithout departing from the scope of the invention, it is intended thatall matter contained in the above description or shown in theaccompanying drawings be interpreted as illustrative and not in alimiting sense.

It is also to be understood that the following claims are to cover allgeneric and specific features of the invention described herein, and allstatements of the scope of the invention which, as a matter of language,might be said to fall therebetween.

We claim:
 1. A spinal connector for connecting a first rod and a secondrod, comprising: a housing defining a first bore hole for receiving aportion of the first rod, the first bore hole extending along a firstlongitudinal axis and a second bore hole for receiving a portion of thesecond rod, the second bore hole extending along a second longitudinalaxis, wherein the first longitudinal axis and the second longitudinalaxis are generally parallel; a set screw for securing at least one ofthe first rod within the first bore hole and the second rod within thesecond bore hole; a rod seat component disposed in the housing forseating at least one of the first rod in the first bore hole and thesecond rod in the second bore hole, wherein the rod seat componentcomprises a top surface and a bottom surface generally opposite the topsurface, the top surface includes a groove that is sized and configuredto receive at least a portion of one of the first rod and the secondrod, and wherein the groove defines a minor arc.
 2. The spinal connectorof claim 1 wherein the rod seat component comprises a compression clip.3. The spinal connector of claim 2 wherein the compression clip isdisposed between at least a portion of the housing and at least one ofthe first rod and the second rod.
 4. The spinal connector of claim 2,wherein the compression clip is an arc-shaped component.
 5. The spinalconnector of claim 1, wherein the housing comprises a first housingcomponent defining the first bore hole and a second housing componentmovably coupled to the first housing component and defining the secondbore hole, the first housing component comprising a coupling rodextending in a direction that is transverse to the first longitudinalaxis and the second housing component including a coupling holeconfigured to receive the coupling rod.
 6. The spinal connector of claim5, wherein the rod seat component comprises a compression clip disposedin the second housing component.
 7. The spinal connector of claim 5,wherein the compression clip is an arc-shaped component.
 8. The spinalconnector of claim 7, wherein the compression clip forms a channel thatis sized and configured to receive at least a portion the coupling rod.9. The spinal connector of claim 8, wherein the compression clip isdisposed between the coupling rod and at least one of the first rod andthe second rod.
 10. The spinal connector of claim 5, wherein the firstlongitudinal axis is configured to be offset in a sagittal plane fromthe second longitudinal axis by a predetermined offset distance when thespinal connector is implanted in a patient.
 11. The spinal connector ofclaim 10, wherein the first longitudinal axis is configured to be offsetin a sagittal plane from the second longitudinal axis by a variableoffset distance when the spinal connector is implanted in a patient. 12.The spinal connector of claim 5, wherein the first housing componentincludes a first set of external teeth on an outer surface thereof andthe second housing component includes a second set of external teeth onan outer surface thereof.
 13. The spinal connector of claim 12, whereinthe first set of external teeth and the second set of external teeth areconfigured to interlock at a plurality of discrete positions.
 14. Thespinal connector of claim 5, wherein the coupling rod includes a firstset of teeth on an outside surface and the coupling hole includes asecond set of teeth on an inside surface configured to contact the firstset of teeth of the coupling rod.
 15. The spinal connector of claim 5,further comprising a clamping mechanism configured to secure the firsthousing component in a selected position relative to the second housingcomponent.
 16. The spinal connector of claim 5, wherein the first borehole is formed by a pair of opening holes extending along the firstlongitudinal axis and having centers which are offset along a centralaxis.
 17. The spinal connector of claim 16, wherein one of the openingholes is sized to provide an interference fit between the first housingcomponent and the first spinal rod.
 18. The spinal connector of claim 5,wherein the second bore hole is formed by a pair of opening holesextending along the second longitudinal axis and having centers whichare offset along a central axis.
 19. The spinal connector of claim 18,wherein one of the opening holes is sized to provide an interference fitbetween the second housing component and the second spinal rod.
 20. Thespinal connector of claim 1 wherein the minor arc is less than 180degrees.
 21. The spinal connector of claim 1 wherein the bottom surfaceincludes a concavity.